UNSOLVED PIR sensor does not switch on monitor

[Klinge]

Hello,
I have configured and connected the PIR sensor exactly as described in this explanation from Hardwarepoint (https://hardwarepoint.net/2017/06/diy-smart-mirror/4/). The sensor also worked until a few weeks ago. Since a few weeks the monitor does not switch off.

Today I could finally take care of the problem and went through the installation steps again. Everything looks like it should be. It worked before. After a reboot, the SmartMirror also starts. And now after about 60 seconds the monitor switched off! But now, the monitor does not switch on when I move in front of it! It stays black. In a browser (Port 8080) I can see the MM. This means that the software is running, but the monitor does not turn on.

The status displays the following

pi@raspberrypi:~ $ sudo systemctl status pir.service
● pir.service - Display timeout PIR daemon
Loaded: loaded (/etc/systemd/system/pir.service; enabled; vendor preset: enab
Active: active (running) since Wed 2020-03-18 09:01:51 CET; 2h 39min ago
Main PID: 1782 (python)
Tasks: 2 (limit: 2200)
Memory: 2.2M
CGroup: /system.slice/pir.service
└─1782 python /usr/local/sbin/pir

Mar 18 09:01:51 raspberrypi systemd[1]: Started Display timeout PIR daemon.
Mar 18 09:01:52 raspberrypi pir[1782]: display_power=1
Mar 18 09:02:51 raspberrypi pir [1782]: display_power=0

It would be really great if someone could help me.

Thanks in advance.
Klinge